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    <script>

        // 先声明后付制
        var x ;
        x = 10 ;


        // 声明即赋值
        var x = 10 ;



        // var a = 1 ;
        // var b = 2 ;
        // var c = 3 ;
        // 多个变量声明使用逗号隔开
        var a = 1 , b = 2 , c = 3 ;

        console.log(a);

        // 变量名区分大小写
        // console.log(A) ;   // A is not defined 

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